Fault Phenomenon: XCMG HB52K main pump is quiet when cold. During high-pressure pumping (operating temperature), the main pump whines, pressure fluctuates, and eventually loses power.

Troubleshooting Process:
– Checked hydraulic oil level: level normal, no foam.
– Checked suction filter: filter not clogged.
– Checked coupling: coupling elastic element intact.
– Measured main pump housing pressure at operating temperature: found excessive housing pressure.

Root Cause: The main pump piston return plate is worn, causing increased clearance and noise under thermal conditions.

Required Parts: Main pump piston assembly and return plate.